Linear vibrator

ABSTRACT

There is provided a linear vibrator including a fixing unit having a magnet in an inner space of a certain size, the magnet generating magnetic force; a vibration unit including a coil disposed to face the magnet and generating electromagnetic force by interaction with the magnet, and a holder coupled with a surface of the coil and fixedly supporting a mass body which vibrates; and an elastic member coupled with the holder and the fixing unit and providing elastic force to the vibration unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2010-0048815 filed on May 25, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a linear vibrator, and moreparticularly, to a linear vibrator achieving stable linear vibrations bypreventing vibrations in a horizontal direction.

2. Description of the Related Art

In recent years, a personal mobile terminal having a large liquidcrystal display (LCD) screen for a user's convenience has beenincreasingly released onto the market. In line with this trend, a touchscreen type display device has been greatly favored, and a vibrationmotor has been used so as to generate vibrations when a touch is appliedto a touch screen.

A vibration motor transforms electrical energy into mechanical energyusing a principle of generating electromagnetic force, is mounted on apersonal mobile terminal, and is used for silent call receptionnotification.

According to the related art, rotatory power is generated to rotate arotational part of an unbalance mass, thereby obtaining mechanicalvibrations. In this case, rotatory power is generated such that it issubjected to a rectifying action through a brush and a contact point ofa commutator (or rectifier) to obtain mechanical vibrations.

However, in the brush type structure using a commutator, when the motorrotates, the brush passes through a gap between segments of thecommutator, causing mechanical friction and an electrical spark,producing foreign objects and thereby shortening the life span of themotor.

In addition, because voltage is applied to the motor by using a momentof inertia, time is taken to reach a target amount of vibrations, so itis difficult to implement vibrations suitable for a touch screen.

In order to overcome such disadvantages in terms of the life span andresponse of the motor and implement the vibration function of the touchscreen, a linear vibrator is increasingly being used.

A linear vibrator, rather than using the rotational principle of themotor, uses the following principle: when electromagnetic force,obtained by using a spring installed inside a vibration motor and a massbody hung on the spring, is generated periodically in conformity with aresonance frequency, resonance is caused, thereby generating vibrations.

However, in a case in which the mass body performs an abnormal operationor unstable vibrations due to an external impact, this impact affectsthe coupling portion of the spring and the mass body, and accordinglythis may cause defects such as disconnection of a coil. A vibration unitincluding the spring or the mass body may be separated from its presetposition.

Therefore, techniques for preventing impact induced by an external forceto generate stable linear vibrations are required. Also, a study for alinear vibrator capable of stopping vibrations quickly and stably isurgently needed.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a linear vibrator preventinga vibration unit from making abnormal vibrations and being separatedfrom a preset position thereof due to external force by changing acoupling structure of an elastic member and a holder supporting a massbody.

According to an aspect of the present invention, there is provided alinear vibrator including: a fixing unit having a magnet in an innerspace of a certain size, the magnet generating magnetic force; avibration unit including a coil disposed to face the magnet andgenerating electromagnetic force by interaction with the magnet, and aholder coupled with a surface of the coil and fixedly supporting a massbody which vibrates; and an elastic member coupled with the holder andthe fixing unit and providing elastic force to the vibration unit.

The holder may include a vertical portion being in contact with thesurface of the coil and having a shape of a cylinder, and a horizontalportion extending from an end of the vertical portion in an outerdiameter direction and fixedly supporting the mass body.

The elastic member may be coupled with the horizontal portion.

The holder may include a vertical portion being in contact with thesurface of the coil and having a shape of a cylinder of which a lowerportion is sealed, and a horizontal portion extending from an end of thevertical portion in an outer diameter direction and fixedly supportingthe mass body.

The elastic member may include a plurality of elastic members, each ofwhich is individually coupled with the sealed lower portion of thevertical portion and the horizontal portion.

The elastic member may be coupled with the holder by welding.

The elastic member and the holder may be formed of the same material.

The magnet may be in contact with an inner sealing surface of an upperportion of the fixing unit.

The linear vibrator may further include a damper provided on an innersealing surface of an upper portion of the fixing unit and formed of anelastic material so as to prevent a contact of the fixing member and thevibration unit induced by linear movements of the vibration unit.

The linear vibrator may further include a lower plate provided on alower surface of the magnet so as to smoothly form a magnetic flux underthe magnet by passing through the coil.

The linear vibrator may further include a magnetic fluid provided to agap between the magnet and the coil so as to allow for smooth verticalmovements of the vibration unit.

The elastic member may be at least any one of a coil spring or a platespring.

The fixing unit may include a flexible printed circuit board applyingpower to the coil, and the elastic member may be coupled with the holderand the flexible printed circuit board.

The fixing unit may include an upper case having the magnet generatingthe magnetic force in an inner space of a certain size and a lower casemounted on a lower portion of the upper case so as to cover the innerspace, and the elastic member may be coupled with the holder and thelower case.

The lower case may include a flexible printed circuit board applyingpower to the coil, and the elastic member may be coupled with the holderand the flexible printed circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an exploded perspective view schematically illustrating alinear vibrator according to an exemplary embodiment of the presentinvention;

FIG. 2 is a cross-sectional view schematically illustrating a linearvibrator according to an exemplary embodiment of the present invention;

FIG. 3 is a cut-out perspective view schematically illustrating a holderprovided in a linear vibrator according to an exemplary embodiment ofthe present invention;

FIG. 4 is a cross-sectional view schematically illustrating a linearvibrator according to another exemplary embodiment of the presentinvention;

FIG. 5 is an exploded perspective view schematically illustrating thecoupling of a holder, an elastic member and a lower case provided in alinear vibrator according to another exemplary embodiment of the presentinvention; and

FIG. 6 is a cross-sectional view schematically illustrating a linearvibrator according to another exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art.

Throughout the drawings, the same reference numerals will be used todesignate the same or like elements.

FIG. 1 is an exploded perspective view schematically illustrating alinear vibrator according to an exemplary embodiment of the presentinvention. FIG. 2 is a cross-sectional view schematically illustrating alinear vibrator according to an exemplary embodiment of the presentinvention. FIG. 3 is a cut-out perspective view schematicallyillustrating a holder provided in a linear vibrator according to anexemplary embodiment of the present invention.

With reference to FIGS. 1 through 3, a linear vibrator 100 may include afixing unit 140, a magnetic field unit 120, a vibration unit 130 and anelastic member 90.

The fixing unit 140 may be sealed such that an upper case 10 is anaccommodation part having an internal space of a certain size and itslower portion being open downwardly is sealed by a lower case 15.

Here, the upper and lower cases 10 and 15 may form an accommodationspace of the magnetic field unit 120, the vibration unit 130, and thelike to be described below. The upper and lower cases 10 and 15 may beintegrally formed.

The magnetic field unit 120 may include a magnet 30 and a lower plate40. The magnet 30 may be in contact with an inner sealing surface of theupper portion of the upper case 10.

The magnet 30 may be a cylindrical permanent magnet having upper andlower portions magnetized to have different polarities in a verticaldirection to generate a magnetic force having a predetermined magnitude.The magnet may be bonded by a bonding material so as to be fixed to theinner sealing surface of the upper portion of the upper case 10.

The lower plate 40 may be provided on a lower surface of the magnet 30so as to smoothly form a magnetic flux under the magnet 30 by passingthrough a coil 60 generating electromagnetic force through interactionwith the magnet 30.

Also, a magnetic fluid 50 may be coated between the coil 60 and theouter circumferential surfaces of the magnet 30 and the lower plate 40.The magnetic fluid 50 may prevent the abnormal vibrations of thevibration unit 130 to be descried below.

That is, the magnetic fluid 50 may be provided in a gap formed betweenthe magnet 30 and the coil 60 so as to allow for smooth verticalmovements of the vibration unit 130. When the vibration unit 130 causeshorizontal vibrations in an event that it vibrates from side to side dueto an external impact, the magnetic fluid 50 may prevent the horizontalvibrations, allow the vibration unit 130 to vibrate in a linear manner,and prevent a minute vibration phenomenon.

The magnetic fluid 50 is a material characterized by focusing on themagnetic flux of the magnet 30. When the magnetic fluid 50 is applied toa surface of the magnet 30, the magnetic fluid 50 may focus on aposition where the magnetic flux of the magnet 30 is generated tothereby form a ring shape.

Here, the magnetic fluid 50 is obtained by stably dispersing magneticpowder in a colloid shape in a liquid and then adding a surfactantthereto to prevent the magnetic powder from being precipitated orcoagulated due to gravitation or a magnetic field. For example, themagnetic fluid 50 may include a magnetic fluid obtained by dispersingtriiron tetroxide or iron-cobalt alloy molecules in oil or water and,recently, a magnetic fluid obtained by dispersing cobalt in toluene.

The magnetic powder is ultrafine particle powder, has Brownian motionpeculiar to ultrafine particles, and has the characteristics that theconcentration of the magnetic powder particles in the fluid is uniformlymaintained even when an external magnetic field, gravitation,centrifugal force, etc., is applied thereto.

Also, the magnetic fluid 50 fills a gap between an outer surface of themagnet 30 and an inner surface of a hollow of the coil 60, therebyallowing the vibration unit 130 to smoothly vibrate or slide.

The vibration unit 130 may include the coil 60, a holder 70 and a massbody 80. The vibration unit 130 may vibrate vertically by the use of theelastic member 90 to be described below.

The coil 60 may be disposed to face the magnet 30, and part of themagnet 30 may be inserted into a space provided by the coil 60.

Also, the coil 60 may be coupled with an inner surface of a hollow ofthe holder 70. When current of a certain frequency is applied to thecoil 60, a magnetic field may be generated around the coil 60.

Here, when electromagnetic force is formed, the magnetic flux passingthrough the coil 60 from the magnet 30 is directed horizontally and themagnetic field generated by the coil 60 is formed vertically, so thatthe vibration unit 130 vibrates vertically. Accordingly, the directionof magnetic flux of the magnet 30 is perpendicular to the vibrationdirection of the vibration unit 130.

That is, when electromagnetic force having a frequency equivalent to anatural frequency of the vibration unit 130 is applied thereto, thevibration unit 130 may develop resonance vibrations to thereby obtainthe maximum amount of vibrations. Here, the natural frequency of thevibration unit 130 is affected by the mass of the vibration unit 130 andthe modulus of elasticity of the elastic member 90.

The holder 70 may be coupled with an outer circumferential surface ofthe coil 60, fixedly support the mass body 80 which vibrates, and have ashape of a hollow cylinder whose upper and lower surfaces are open.

Specifically, the holder 70 may include a vertical portion 72 coupledwith the outer circumferential surface of the coil 60 by being incontact therewith and having a shape of a cylinder, and a horizontalportion 74 extending from an end of the vertical portion 72 in an outerdiameter direction.

An outer circumferential surface of the vertical portion 72 and an uppersurface of the horizontal portion 74 may be in contact with the massbody 80 to fixedly support the mass body 80, and a lower surface of thehorizontal portion 74 may be coupled with the elastic member 90 to bedescribed below.

Also, the holder 70 may be formed of iron (Fe). This is intended tofacilitate and secure the coupling of the holder 70 and the elasticmember 90 by allowing the holder 70 to be formed of the same material asthat of the elastic member 90.

However, the material of the holder 70 and the elastic member 90 is notlimited to iron (Fe). The holder 70 and the elastic member 90 may beformed of any material, as long as the material allows for thefacilitation of secure coupling.

Here, the holder 70 may have an upper coupling portion 110 a on a bottomsurface thereof such that the upper coupling portion 110 a is in contactwith the elastic member 90. The upper coupling portion 110 a may be aportion where the bottom surface of the holder 70 and the elastic member90 are coupled by welding.

The mass body 80 is a vibration body being coupled with the outersurface of the vertical portion 72 and the upper surface of thehorizontal portion 74 and vibrating vertically. When the mass body 80vibrates vertically, the mass body 80 may have an outer diameter smallerthan an inner diameter of an inner surface of the upper case 10 to allowthe mass body 80 to vibrate within the fixing unit 140 without anycontact.

In this manner, a gap of a certain size may be formed between the innersurface of the upper case 10 and an outer surface of the mass body 80.

The mass body 80 may be formed of nonmagnetic or paramagnetic substancesthat are not affected by the magnetic force generated from the magnet30.

Therefore, the mass body 80 may be formed of a material, such astungsten, having a greater specific gravity than iron. This is intendedto maximize the amount of vibrations by controlling a resonancefrequency due to an increase in the mass of the vibration unit 130within a limited volume.

However, the material of the mass body 80 is not limited to tungsten.The mass body 80 may be formed of various materials according to adesigner's intention.

Also, the mass body 80 may be expanded such that the side surfacethereof has a further increased mass. This is also intended to maximizethe amount of vibrations by increasing the mass within a limited volume.

In order to compensate for the natural frequency of the linear vibrator100, the mass body 80 may include a space into which a sub-mass body isfurther inserted, thereby allowing its mass to be increased anddecreased.

As described above, the elastic member 90 is coupled with the holder 70and the lower case 15 and provides elastic force to the vibration unit130. Also, the elastic member 90 may include a plurality of elasticmembers. The modulus of elasticity of the elastic member 90 may affectthe natural frequency of the vibration unit 130.

One end of the elastic member 90 may be coupled with the bottom surfaceof the horizontal portion 74 of the holder 70, thereby forming the uppercoupling portion 110 a.

The upper coupling portion 110 a may be a portion where the one end ofthe elastic member 90 and the bottom surface of the horizontal portion74 are coupled by welding. As described above, the elastic member 90 andthe holder 70 may be formed of the same material, so that the couplingthereof by the welding may be facilitated and secured.

Here, the elastic member 90 may be any one of a coil spring and a platespring. An example of using the plate spring will be described withreference to FIGS. 4 and 5.

However, the elastic member 90 is not limited to the above-mentionedspring, and it may have various forms as long as it provides elasticforce.

The other end of the elastic member 90 may be coupled with a surface ofthe lower case 15 by welding, thereby forming a lower coupling portion110 b.

A flexible printed circuit board (not shown) may be provided on an uppersurface of the lower case 15 so as to make electrical connections withthe coil 60. The other end of the elastic member 90 may be coupled withthe printed circuit board by welding to thereby form the lower couplingportion 110 b.

Meanwhile, a damper 20 may be formed on the inner sealing surface of theupper portion of the upper case 10. The damper 20 may have a structureaccommodating the magnet 30.

The damper 20 may be formed of elastic material so as to prevent contactbetween the vibration unit 130 and the upper case 10 induced by thelinear movements of the vibration unit 130. The damper 20 may preventtouch noise that may occur in a case in which the vibration unit 130excessively vibrates to be in contact with the upper case 10, and alsoprevent abrasion of the vibration unit 130.

Also, the damper 20 may absorb an external impact to extend the lifespan of the linear vibrator 100. The damper 20 may be formed of variousmaterials, such as rubber, cork, propylene, or the like, capable ofabsorbing the impact.

FIG. 4 is a cross-sectional view schematically illustrating a linearvibrator according to another exemplary embodiment of the presentinvention. FIG. 5 is an exploded perspective view schematicallyillustrating the coupling of a holder, an elastic member and a lowercase provided in a linear vibrator according to another exemplaryembodiment of the present invention.

With reference to FIGS. 4 and 5, the linear vibrator 100 according toanother exemplary embodiment of the invention has the same constitutionand effect as those of the above-described embodiment with the exceptionof the elastic member 90, so a detailed description thereof will beomitted.

The elastic member 90 may be a plate spring, and a portion thereof beingprotruded upwardly may be coupled with the horizontal portion 74 of theholder 70 by welding.

That is, the protruded portion and the horizontal portion 74 may becoupled to form the upper coupling portion 110 a. In order to facilitateand secure the coupling of the protruded portion and the horizontalportion 74 by welding, the holder 70 and the elastic member 90, i.e.,the plate spring, may be formed of the same material.

A lower portion of the plate spring may be coupled with a surface of thelower case 15 by welding, thereby forming the lower coupling portion 110b.

A flexible printed circuit board (not shown) may be provided on theupper surface of the lower case 15 so as to make electrical connectionswith the coil. The lower portion of the elastic member 90 may be coupledwith the printed circuit board by welding to thereby form the lowercoupling portion 110 b.

FIG. 6 is a cross-sectional view schematically illustrating a linearvibrator according to another exemplary embodiment of the presentinvention.

With reference to FIG. 6, the linear vibrator 100 according to anotherexemplary embodiment of the invention has the same constitution andeffect as those of the above-described embodiment with the exception ofa coupling structure of the elastic member 90 and the holder 70, so adetailed description thereof will be omitted.

The holder 70 may include the vertical portion 72 being in contact witha surface of the coil 60 and having a shape of a cylinder whose lowerportion is sealed, and the horizontal portion 74 extending from an endof the vertical portion 72 in an outer diameter direction.

Therefore, one end of the elastic members 90 may be individually coupledwith a bottom surface of the horizontal portion 74 and a bottom surfaceof the sealed lower portion of the vertical portion 72 by welding andthe other end thereof may be coupled with a surface of the lower case15.

The holder 70 may fixedly support the mass body 80 and the coil 60 andthe elastic member 90 may be coupled with the holder 70 and the fixingunit 140 by welding, thereby preventing the vibration unit from makingabnormal vibrations and being separated from its preset portion due toan external force. Also, linear vibrations having greater stability maybe achieved by preventing the abnormal vibrations of the vibration unit30.

As set forth above, in a linear vibrator according to exemplaryembodiments of the invention, the separation of an elastic member and avibration unit from their preset positions due to an external force maybe prevented.

In addition, a linear vibrator according to exemplary embodiments of theinvention may prevent a vibration unit from making abnormal vibrationsto thereby achieve more stable linear vibrations and allow the vibrationunit to stop the vibrations quickly and stably.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1. A linear vibrator comprising: a fixing unit having a magnet in aninner space of a certain size, the magnet generating magnetic force; avibration unit including a coil disposed to face the magnet andgenerating electromagnetic force by interaction with the magnet, and aholder coupled with a surface of the coil and fixedly supporting a massbody which vibrates; and an elastic member coupled with the holder andthe fixing unit and providing elastic force to the vibration unit. 2.The linear vibrator of claim 1, wherein the holder comprises: a verticalportion being in contact with the surface of the coil and having a shapeof a cylinder; and a horizontal portion extending from an end of thevertical portion in an outer diameter direction and fixedly supportingthe mass body.
 3. The linear vibrator of claim 2, wherein the elasticmember is coupled with the horizontal portion.
 4. The linear vibrator ofclaim 1, wherein the holder comprises: a vertical portion being incontact with the surface of the coil and having a shape of a cylinder ofwhich a lower portion is sealed; and a horizontal portion extending froman end of the vertical portion in an outer diameter direction andfixedly supporting the mass body.
 5. The linear vibrator of claim 4,wherein the elastic member comprises a plurality of elastic members,each of which is individually coupled with the sealed lower portion ofthe vertical portion and the horizontal portion.
 6. The linear vibratorof claim 1, wherein the elastic member is coupled with the holder bywelding.
 7. The linear vibrator of claim 1, wherein the elastic memberand the holder are formed of the same material.
 8. The linear vibratorof claim 1, wherein the magnet is in contact with an inner sealingsurface of an upper portion of the fixing unit.
 9. The linear vibratorof claim 1, further comprising a damper provided on an inner sealingsurface of an upper portion of the fixing unit and formed of an elasticmaterial so as to prevent a contact of the fixing member and thevibration unit induced by linear movements of the vibration unit. 10.The linear vibrator of claim 1, further comprising a lower plateprovided on a lower surface of the magnet so as to smoothly form amagnetic flux under the magnet by passing through the coil.
 11. Thelinear vibrator of claim 10, further comprising a magnetic fluidprovided to a gap between the magnet and the coil so as to allow forsmooth vertical movements of the vibration unit.
 12. The linear vibratorof claim 1, wherein the elastic member is at least any one of a coilspring or a plate spring.
 13. The linear vibrator of claim 1, whereinthe fixing unit includes a flexible printed circuit board applying powerto the coil, and the elastic member is coupled with the holder and theflexible printed circuit board.
 14. The linear vibrator of claim 1,wherein the fixing unit includes an upper case having the magnetgenerating the magnetic force in an inner space of a certain size and alower case mounted on a lower portion of the upper case so as to coverthe inner space, and the elastic member is coupled with the holder andthe lower case.
 15. The linear vibrator of claim 14, wherein the lowercase includes a flexible printed circuit board applying power to thecoil, and the elastic member is coupled with the holder and the flexibleprinted circuit board.